netdev - [PATCH 4/4] net: ll_temac: Avoid ndo_start_xmit returning NETDEV_TX

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Date:   Fri, 18 Jun 2021 12:52:38 +0200
From:   Esben Haabendal <esben@...nix.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Zhang Changzhong <zhangchangzhong@...wei.com>,
        Andrew Lunn <andrew@...n.ch>, Michael Walle <michael@...le.cc>,
        Wang Hai <wanghai38@...wei.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] net: ll_temac: Avoid ndo_start_xmit returning NETDEV_TX_BUSY

As documented in Documentation/networking/driver.rst, the ndo_start_xmit
method must not return NETDEV_TX_BUSY under any normal circumstances, and
as recommended, we simply stop the tx queue in advance, when there is a
risk that the next xmit would cause a NETDEV_TX_BUSY return.

Signed-off-by: Esben Haabendal <esben@...nix.com>
---
 drivers/net/ethernet/xilinx/ll_temac_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index cc482ee36501..9a13953ea70f 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -942,6 +942,11 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	wmb();
 	lp->dma_out(lp, TX_TAILDESC_PTR, tail_p); /* DMA start */
 
+	if (temac_check_tx_bd_space(lp, MAX_SKB_FRAGS + 1)) {
+		netdev_info(ndev, "%s -> netif_stop_queue\n", __func__);
+		netif_stop_queue(ndev);
+	}
+
 	return NETDEV_TX_OK;
 }
 
-- 
2.32.0